DESCRIPTION (authors abstract): We are interested in understanding how NFkB Rel signaling pathways are regulated in the innate immune response. In mammals, NFkB is activated in response to a great number of different stimuli in the immune response and in turn can activate an impressive range of target genes. Multiple ligands and their specific receptors activate many of the same signaling components that act upstream of the Rel proteins. With the number of components that are shared between Rel signaling pathways, how is specificity in Rel signaling achieved at the molecular level? We study this question in Drosophila. This allows us to take advantage of the genetics and the genome sequence information to study a highly conserved signaling pathway in a simpler organism. The specific aims of this proposal are: 1. To identify novel genes required for specific Rel signaling pathways by map-based cloning of the ird1 and ird20 genes. These two genes were identified in a genetic screen for immune response deficient mutants. These genes are necessary for activation of two out of the three known Rel proteins. By cloning and characterizing these genes, we hope to understand how they are specific for one pathway and not the other. 2. To understand how one IkB, Cactus, can differentially inhibit multiple Rel proteins. We will test if different forms of Cactus preferentially associate with different Rel proteins and if Cactus is differentially phosphorylated when it is complexed with different Rel proteins. 3. To understand how one receptor, Toll can mediate different pathogenic signals. We find that Toll is required for responses to lipopolysaccharide and mannans. We will look at mutations for other Rel signaling components and other Toll-like receptors to see if they are required for LPS and/or mannan responses. This may give insight to how different pathways can use the same receptor. These studies should lead to a better understanding of how specific Rel signaling pathways are regulated. Understanding Rel signaling should help in the development of therapies for inflammation, endotoxic shock and infectious diseases.